The present invention relates generally to accumulator fuel injection systems and relates more particularly to a new and improved accumulator injector which provides improved control of the fuel injection rate.
Accumulator-type nozzles or injectors generally function in a manner wherein pressurized fuel supplied from a pump accumulates within a chamber of the injector. A needle valve is responsive to opposing fuel pressure exerted forces and upon release of pressure is lifted to inject fuel into an engine cylinder. A characteristic of accumulator-type injectors is a so-called negative rate of injection wherein the rate of fuel injection at the commencement of the fuel injection is significantly greater than the rate of fuel injection at the termination of the injection. The negative rate of injection characteristics may result in excessive noise and an increase in exhaust pollutants from the internal combustion engine. It is a principal aim of the present invention to provide a new and improved accumulator injector which ameliorates the negative injection rate characteristics common to accumulator injectors and produces a pilot injection or two phase injection.